DESCRIPTION: The survival and transparency of the lens depend on intercellular communication through lens fiber gap junction channels formed of two connexins, Cx46 and Cx50. Families have been identified with inherited cataracts associated with mutations of both of these connexins. We have established transfected cell and transgenic mouse expression systems for the study of normal and mutated lens connexins. Our recent studies show that the cloned human mutant connexins do not make functional gap junction channels. Moreover, in stably transfected cells, our data regarding fiber connexin mutants (including Cx50P88S, Cx46fs380, and Cx50P88Q) show that they do not properly assemble into gap junctions, because they are retained in the cytoplasm (at different sites) and are not properly degraded. This project will focus on testing the central question: How do perturbations of gap junctions (especially mutation of the fiber connexins) affect lens development, structure, and function? We will use immuno- and bio-chemical techniques to examine the cellular processing of Cx50P88S, Cx46fs380, and other connexin mutants in stably transfected cells to ask: What are the cellular mechanisms and consequences of the abnormal trafficking and accumulation of cataract-associated mutant connexins? (Aim 1) We will develop and analyze transgenic mice that express the wild-type human Cx50 and ES cell-derived mice that express the mutant, Cx46fs380. We will use them to ask: Can the pathogenesis of human cataracts due to over-expression of a wild-type connexin or due to expression of a mutant connexin be elucidated in mouse models? Do the lenses of these mice exhibit alterations of connexin distribution/trafficking and function similar to those seen in transfected cells? What are the consequences of expression of Cx46fs380 upon lens membranes, intercellular communication, other lens components and transparency? (Aim 2) These studies will elucidate the pathogenesis of cataracts and the importance of lens fiber connexins for maintaining lens transparency.